Its always better to do things fair (in that way you will also be better at this game because you would have played more matches to unlock everything by yourself) but if you prefer to go the easy way then here are some codes that will make your life easier.
Enter those codes at the passwords menu (in options)
Alternative Tamers
While selecting a digimon press and hold L1 + L2 + R1 + R2 and down. This will only work with some digimons and it doesn't affect your gameplay in anyway; just the tamer of the digimon will appear to be different.